OP0021 STRATIFICATION OF PATIENTS WITH SJÖGREN’S SYNDROME BY JOINT MULTI-MODAL ANALYSIS OF CIRCULATING B CELLS
Authors: G. Arvidsson, P. Czarnewski, A. Johansson, A. Raine, J. Imgenberg-Kreuz, J. Nordlund, G. Nordmark, A. C. Syvänen
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> B cells are important in the pathogenesis of primary Sjögren's syndrome (pSS) with hypergammaglobulinemia, SSA/SSB autoantibodies and an increased risk of B cell lymphoma [1]. Patients with pSS positive for SSA/SSB autoantibodies are more prone to systemic disease manifestations and adverse outcomes. Only few studied have investigated peripheral blood mononuclear cells at single cell resolution and primarily reported differences in the T cell compartment while the B cells were only briefly considered [2,3]. <h3>Objectives</h3> We aimed to determine the role of peripheral B cell subtype composition, gene expression and B cell receptor (BCR) usage in patients with pSS stratified for SSA/SSB antibodies. <h3>Methods</h3> Over 230 000 B cells were isolated by negative selection from peripheral blood of 24 pSS patients (n=6 SSA+, n=8 SSA- and n=10 SSA and SSB+ (SSAB)) and four healthy controls. Single cell gene expression and targeted BCR libraries were generated and processed for RNA and VDJ sequencing. <h3>Results</h3> Gene expression-based clustering and cell annotation defined 16 B cell subtypes. We show that pSS patients have a heterogeneous circulating B cell composition, with SSAB patients presenting the highest and lowest proportion of naïve and memory B cells, respectively. Interferon-induced genes were upregulated across all B cell subtypes with the highest levels in the SSAB group. Differential usage of Immunoglobulin Heavy Chain (<i>IGH</i>) genes, showed that memory B cells from SSAB patients displayed a higher proportion of <i>IGHM</i> expressing cells and cells with unmutated VDJ transcripts, including <i>IGHV1-69</i> and <i>IGHV4-34</i>, compared to other pSS patient groups and controls, indicating altered somatic hypermutation and class switching processes. Comparison with previous studies revealed heterogeneous clonotype pools, with little overlap in CDR3 sequences. Joint principal component analysis using scRNA-seq and scVDJ-seq data including B cell subtype composition, IFN-score, <i>IGH</i> constant gene usage, <i>IGHV</i> usage and VDJ mutation status allowed unsupervised stratification pSS patients that correlated to disease manifestations and antibody status. <h3>Conclusion</h3> Combining single cell gene expression and VDJ sequence data we describe heterogeneity and molecular characteristics in B cells from pSS patients with different autoantibody profiles. Our results may provide clues to intrinsic differences in B cells that affect the phenotype and outcome, and allow stratification of pSS patients at improved resolution. <h3>References</h3> [1] Nocturne G, Mariette X. B cells in the pathogenesis of primary Sjogren syndrome. Nat Rev Rheumatol 2018;14:133-45. [2] Hong X, et al. Single-Cell RNA Sequencing Reveals the Expansion of Cytotoxic CD4(+) T Lymphocytes and a Landscape of Immune Cells in Primary Sjogren's Syndrome. Front Immunol 2020;11:594658. [3] Hou X, et al. Analysis of Gene Expression and TCR/B Cell Receptor Profiling of Immune Cells in Primary Sjogren's Syndrome by Single-Cell Sequencing. J Immunol 2022;209:238-49. <h3>Acknowledgements</h3> We thank Rezvan Kiani Dehkordi for collecting patient and control samples. <h3>Disclosure of Interests</h3> None Declared.